1. Field of the Invention
The present invention relates to power tools having lights and methods for operating such power tools. More particularly, the present invention relates to power tools having lights that can light a work area and are more convenient to use than known power tools.
2. Description of the Related Art
Known power tools having lighting devices generally provide a light that operates separately from the tool. That is, the lighting circuit is electrically separate from the motor operation circuit and thus, the light can be turned on even when the tool is not being used. Thus, if the power tool is powered by rechargeable batteries and the light is left on when the power tool is not being used, the rechargeable batteries may be completely discharged and possibly permanently damaged.
FIG. 9 shows a circuit taught by German Patent No. DE 3831344 C2 to control the operation of a light 34 for another type of power tool, in which the lighting circuit and the motor 18 can be operated by a single switch. This known power tool has a switch 76 that can be pushed by the user to activate the motor 18 and the same switch 76 also can control the light. Specifically, according to this German reference, switch 76 is a two-stage push switch.
If the switch 76 is pushed to an intermediate position, the lighting contact S1 will close (on state) and the light 34 will turn on. The motor contact S2 is open (off state), such that the motor 18 does not operate while the switch 76 is in the intermediate position. Therefore, the user can utilize the light in a manner similar to a flashlight in order to position the power tool with respect to the work piece (i.e., a board) while the motor 18 is stopped.
If the two-stage switch 76 is pushed further, the motor contact S2 will close (on state) and thus, the motor 18 will begin to rotate. As a result, the user can begin performing the intended power tool operation, such as driving a screw using a powered screwdriver.
A timer circuit 102 is provided to turn off the light 34 after a predetermined period of time. Thus, the user is not required to manually turn off the light. This timer circuit 102 starts the timing operation when the motor contact S2 closes (i.e. beginning of the motor on state) and opens (i.e. disconnects) the second lighting contact K1 after the predetermined period of time has passed, thereby turning off the light 34. German Patent No. DE 3831344 C2 also describes another design in which the timer circuit 102 starts the timing operation when the lighting contact S1 is closed (turned on). Thus, the light 34 can be turned off either (1) after a pre-determined period of time has passed since the motor 18 began to rotate or (2) after a pre-determined period of time has passed since the light 34 was turned on. As a result, the light 34 will automatically turn off and the user is not required to manually turn off the light 34.
In this known power tool, the switch 76 must be pressed to the intermediate position in order to maintain the light 34 in the on state. Therefore, the operator must adjust the position of the power tool and/or workpiece while holding the switch 76 in the intermediate position. In other words, the user can not remove his/her finger from the switch while adjusting the position and angle of the power tool and/or work. Therefore, the user""s hand may become fatigued if repeated screw-driving operations are required.
If the stroke length of the switch 76 is long, it may be easier to hold the switch in an intermediate position in order to turn on the light 34 while preventing the motor 18 from unintentionally starting. However, the user must move his or her finger over a longer range of motion during the lighting and screw-driving operations, thereby causing fatigue. On the other hand, if the stroke length of the switch 76 is short, it may be easier to start the power tool operation, but it may become more difficult to hold the switch in the intermediate position in order to light the work area before being the power tool operation.
Furthermore, the known power tool requires a two-stage push-type switching device and cannot use a common, inexpensive single stage on-off switching device, thereby raising manufacturing costs.
It is an object of the present invention to teach improved power tools having lighting devices that are easy to operate and can be manufactured with common, inexpensive on-off switching devices.
It is another object of the present invention to teach methods for using such easily operated power tools having lighting devices.
In one aspect, power tools are taught that have a lighting circuit, in which the light and the power tool motor are simultaneously turned on by a single switch. Thus, if the operation of the motor is initiated, the light will turn on. Preferably, a timer is provided to turn off the light at a predetermined time either (1) after the time in which the switch was initially closed (i.e., the on state was initiated) or (2) after the time in which the switch was opened after the motor has started to rotate.
Such power tools can use common, inexpensive, one-stage on-off switches, thereby reducing manufacturing costs. Also, if the present teachings are utilized in a xe2x80x9ccordlessxe2x80x9d power tool (e.g., battery operated tool), the operator is prevented from forgetting to turn off the light and possibly damaging rechargeable batteries, because power tools according to the present teachings will automatically turn off the light.
Because both the motor and light are simultaneously operated, the motor will begin to rotate at the same or substantially the same time that the light turns on. In fact, power tools may be designed such that the light can not be turned on without starting the motor. In such a design, once the switch has been activated in order to simultaneously start both the motor and the light, the switch can be returned to the off position. Returning the switch to the off position will cause the motor to stop, but the light will continue to shine, because a timer is provided. Preferably, the timer is constructed such that the operator can adjust the delay time before the light turns off, so that the operator can determine the appropriate amount of time for the light to remain on after the motor has stopped. The position and angle of the power tool and/or workpiece can thus be adjusted using the light of such a power tool while the motor is stopped. Therefore, such power tools are very convenient and easy to operate.
If the operator is not ready to perform the intended power tool operation when the light is first turned on, the operator can press the switch for a short time in order to turn on the light and then promptly release (turn off) the switch. In such case, even though the switch is in the off position, the light will continue to shine for a predetermined period of time. The operator can therefore adjust the position and angle of the power tool and/or workpiece using the light, but without further operating the motor. After adjusting the position and angle of the power tool, the operator can turn on the motor by pressing the switch again and can use the power tool to perform the desired operation.
According to the present teachings, the operator is not required to move the switch to an intermediate position, thereby simplifying the lighting operation and reducing fatigue. Also, the operator can adjust the position and angle of the power tool and/or work without having to further operate the switch. Thus, such tools are easy to use and inexpensive to manufacture.
In another aspect of the present teaching, the operator preferably can adjust the length of time that the light remains on after the switch has been closed (on state) and then opened (off state). Naturally, if the operator can adjust the delay time, the operator can utilize an optimal time period for operating the light for each particular project and can reduce or prevent wasted power consumption from unnecessary use of the light.
Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims.